Titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index, in which it is surpassed only by a few other materials. TiO2 is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, medicines (i.e. pills and tablets) as well as most toothpastes. In paint, it is often referred to offhandedly as "the perfect white", "the whitest white", or other similar terms. In ceramic glazes titanium dioxide acts as an opacifier and seeds crystal formation. Titanium dioxide has been shown statistically to increase skimmed milk's whiteness, increasing skimmed milk's sensory acceptance score. Titanium dioxide is used to mark the white lines of some tennis courts.
